1,187 research outputs found
Probing the Cluster Mass Distribution using Subaru Weak Lensing Data
We present results from a weak lensing analysis of the galaxy cluster A1689
(z=0.183) based on deep wide-field imaging data taken with Suprime-Cam on
Subaru telescope. A maximum entropy method has been used to reconstruct
directly the projected mass distribution of A1689 from combined lensing
distortion and magnification measurements of red background galaxies.The
resulting mass distribution is clearly concentrated around the cD galaxy, and
mass and light in the cluster are similarly distributed in terms of shape and
orientation. The azimuthally-averaged mass profile from the two-dimensional
reconstruction is in good agreement with the earlier results from the Subaru
one-dimensional analysis of the weak lensing data, supporting the assumption of
quasi-circular symmetry in the projected mass distribution of the cluster.Comment: To appear in Mod. Phys. Lett. A, 8pages, 5 figures, minor typo errors
corrected, Fig.5 modifie
Two-loop two-point functions with masses: asymptotic expansions and Taylor series, in any dimension
In all mass cases needed for quark and gluon self-energies, the two-loop
master diagram is expanded at large and small , in dimensions, using
identities derived from integration by parts. Expansions are given, in terms of
hypergeometric series, for all gluon diagrams and for all but one of the quark
diagrams; expansions of the latter are obtained from differential equations.
Pad\'{e} approximants to truncations of the expansions are shown to be of great
utility. As an application, we obtain the two-loop photon self-energy, for all
, and achieve highly accelerated convergence of its expansions in powers of
or , for .Comment: 25 pages, OUT--4102--43, BI--TP/92--5
BIMA and Keck Imaging of the Radio Ring PKS 1830-211
We discuss BIMA (Berkeley Illinois Maryland Association) data and present new
high quality optical and near-IR Keck images of the bright radio ring PKS
1830-211. Applying a powerful new deconvolution algorithm we have been able to
identify both images of the radio source. In addition we recover an extended
source in the optical, consistent with the expected location of the lensing
galaxy. The source counterparts are very red, I-K=7, suggesting strong Galactic
absorption with additional absorption by the lensing galaxy at z=0.885, and
consistent with the detection of high redshift molecules in the lens.Comment: To be published in the ASP Conference Proceedings, 'Highly Redshifted
Radio Lines', Greenbank, W
Flotation of coal and sulphur from South African ultrafine colliery wastes
Flotation of coal and sulphur from a typical South African ultrafine
colliery waste has been achieved in laboratory-scale batch flotation
tests, using dodecane, kerosene, and oleic acid as coal collectors, and
xanthates to float the sulphide minerals (with the aid of dextrin as a
coal depressant). The use of oleic acid as collector, in conjunction
with MIBC frother, produced a coal yield of 56 per cent (much more
than was obtained with dodecane or kerosene) at an ash content of
18 per cent, from a feed ash of 34.4 per cent; and a low- sulphur
tailings. Sulphide flotation using potassium xanthate (PAX)
recovered 26.3 per cent of the total sulphur in the concentrate.
Staged addition of xanthate increased the total sulphur recovery to
42.1 per cent and reduced the sulphur content of the tailing further
LensPerfect: Gravitational Lens Massmap Reconstructions Yielding Exact Reproduction of All Multiple Images
We present a new approach to gravitational lens massmap reconstruction. Our
massmap solutions perfectly reproduce the positions, fluxes, and shears of all
multiple images. And each massmap accurately recovers the underlying mass
distribution to a resolution limited by the number of multiple images detected.
We demonstrate our technique given a mock galaxy cluster similar to Abell 1689
which gravitationally lenses 19 mock background galaxies to produce 93 multiple
images. We also explore cases in which far fewer multiple images are observed,
such as four multiple images of a single galaxy. Massmap solutions are never
unique, and our method makes it possible to explore an extremely flexible range
of physical (and unphysical) solutions, all of which perfectly reproduce the
data given. Each reconfiguration of the source galaxies produces a new massmap
solution. An optimization routine is provided to find those source positions
(and redshifts, within uncertainties) which produce the "most physical" massmap
solution, according to a new figure of merit developed here. Our method imposes
no assumptions about the slope of the radial profile nor mass following light.
But unlike "non-parametric" grid-based methods, the number of free parameters
we solve for is only as many as the number of observable constraints (or
slightly greater if fluxes are constrained). For each set of source positions
and redshifts, massmap solutions are obtained "instantly" via direct matrix
inversion by smoothly interpolating the deflection field using a recently
developed mathematical technique. Our LensPerfect software is straightforward
and easy to use and is made publicly available via our website.Comment: 17 pages, 18 figures, accepted by ApJ. Software and full-color
version of paper available at http://www.its.caltech.edu/~coe/LensPerfect
Cloning Hubble Deep Fields I: A Model-Independent Measurement of Galaxy Evolution
We present a model-independent method of quantifying galaxy evolution in
high-resolution images, which we apply to the Hubble Deep Field (HDF). Our
procedure is to k-correct all pixels belonging to the images of a complete set
of bright galaxies and then to replicate each galaxy image to higher redshift
by the product of its space density, 1/V_{max}, and the cosmological volume.
The set of bright galaxies is itself selected from the HDF, because presently
the HDF provides the highest quality UV images of a redshift-complete sample of
galaxies (31 galaxies with I<21.9, \bar{z}=0.5, and for which V/V_{max} is
spread fairly). These galaxies are bright enough to permit accurate
pixel-by-pixel k-corrections into the restframe UV (\sim 2000 A). We match the
shot noise, spatial sampling and PSF smoothing of the HDF data, resulting in
entirely empirical and parameter-free ``no-evolution'' deep fields of galaxies
for direct comparison with the HDF. In addition, the overcounting rate and the
level of incompleteness can be accurately quantified by this procedure. We
obtain the following results. Faint HDF galaxies (I>24) are much smaller, more
numerous, and less regular than our ``no-evolution'' extrapolation, for any
interesting geometry. A higher proportion of HDF galaxies ``dropout'' in both U
and B, indicating that some galaxies were brighter at higher redshifts than our
``cloned'' z\sim0.5 population.Comment: 51 pages, 23 figures, replacement includes figures not previously
include
Seed production areas for the global restoration challenge
Wild-collected seed can no longer meet global demand in restoration. Dedicated Seed Production Areas (SPA) for restoration are needed and these require application of ecological, economic, and population-genetic science. SPA design and construction must embrace the ecological sustainability principles of restoration
The effect of FIR emission from SDSS galaxies on the SFD Galactic extinction map
We compare the most successful and widely used map of Galactic dust
extinction, provided by Schlegel, Finkbeiner & Davis (1998; hereafter SFD), to
the galaxy number counts in the Sloan Digital Sky Survey (SDSS)
photometric/spectroscopic DR4 sample. We divide the SDSS survey area into 69
disjoint subregions according to the dust extinction provided by SFD and
compare the surface number density of galaxies in each subregion. As expected,
the galaxy surface number density decreases with increasing extinction but only
for SFD extinction values above about 0.1 to 0.2 magnitudes (depending on the
band). At lower values of the SFD extinction, we find that the sky surface
density of galaxies increases with increasing extinction, precisely the
opposite of the effect expected from Galactic dust. We suggest that the far
infrared (FIR) brightness of the sky in regions of true low dust extinction is
significantly ``contaminated'' by the FIR emission from background galaxies. We
show that such an explanation is both qualitatively and quantitatively
consistent with the available data. Based on this interpretation we conclude
that systematic errors in the SFD extinction map due to extragalactic FIR
emission are quite small, of order hundredths of a magnitude, but nevertheless
statistically detectable. (Abridged)Comment: 23 pages, 14 figures, submitted to PAS
The static quark-antiquark potential in QCD to three loops
The static potential between an infinitely heavy quark and antiquark is
derived in the framework of perturbative QCD to three loops by performing a
full calculation of the two-loop diagrams and using the renormalization group.
The contribution of massless fermions is included.Comment: Latex, 11 pages, 3 figures included. The complete paper, including
figures, is also available via anonymous ftp at
ftp://ttpux2.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/ . Revised version,
essentially identical to the version published in Physical Review Letter
- …